Process for inhibiting rusting



Patented set. 12, E952 FCE raocass ron mnmrrmo nus'rmc ration of Delaware No Drawing. Application January 8, 1949, Serial No. 69,983

3 Claims.

The present invention relates to a process for inhibiting the rusting of metal surfaces, particularly when the metal surfaces are stored or otherwise idle. A further object of this invention is to contact the metal surfaces of an internal combustion engine with a fuel composition comprising gasoline containing tetraethyl lead and an organic halide which of itself is incapable of preventing rust, in admixture with partial esters, formed from a polyhydroxy alcohol and one or more monocarboxylic acids, as rust inhibitors. A more specific object of the present invention is to inhibit rust formation on the metal surfaces of an internal combustion engine, utilizing a gasoline containing tetraethyl lead and an organic halide in admixture with mono, di, and tri alkyl esters of pentaerythritol.

It is well known in the art to employ as fuels for internal combustion engines, gasolines containing tetraethyl lead and an added organic halide which functions as a scavenger agent for the lead. Internal combustion engines utilizing fuels of this character tend to form rust on the interior surfaces, particularly when left idle. The rust forming tendencies are greatly aggravated in the presence of wet or moist air. The problem is particularly acute with respect to aviation engines wherein the normal practice is to have a turnabout period during which time the aviation engine is left in an idle condition. Furthermore, aviation engines are normally stored for periods of time prior to their reinstallation in the plane. It is, therefore, the objects of the present invention to set forth a new improved fuel composition and to outline an improved process for taking internal combustion engines, especially aviation internal combustion engines, out of service.

Various attempts have been made to solve the problem of rust formation on the metal surfaces of internal combustion engines. One method employed is to add various inhibitors to the lubricating oils utilized in the engine crankcases. However, these compounded lubricating oils can only contact certain internal metallic areas of the engine. These oils, do not have ready access to certain internal surfaces of the engine, especially the upper section of the cylinder liner in and near the combustion chamber, where the fuel enters. It is thus, difficult to inhibit these particular sections against rust. Therefore, it is a common and inconvenient practice to spray these sections through the sparkplug holes with a compounded oil containing satisfactory inhibitors. However, neither complete coverage nor even distribution of the inhibited oil over the cylinder liner is secured by this technique of application.

One object of the present invention is to inhibit completely the formation of rust on the surfaces of cylinder liners and those metal parts of the engine to which only the fuel is accessible. This is accomplished by adding to a fuel, such as gasoline containing tetraethyl lead and an organic halide, partial esters formed from a polyhydroxy alcohol and one or more monocarboxylic acids. These esters may be added as single compounds or as mixtures. It has been found that if these esters are added to a fuel in a concentration in the range from about 0.01% to 1.0%, preferably about 0.5% by weight and the fuel composition is passed through an engine prior to storage, the critical metallic surfaces of the engine, including the combustion chamber and the cylinder-liner area within the path of the piston travel will be very satisfactorily protected against the formation of rust.

Although various polyhydroxy alcohols may be employed as for example, dipentaerythritol, polyglycerol, sorbitol, 'polysorbitol, mannitol, partly dehydrated sorbitol (sorbitan), or erythritol, the preferred alcohol is pentaerythritol. The monocarboxylic acids used for esterification should have from about 8-24 carbon atoms per molecule, preferably about 18 carbon atoms per molecule. Satisfactory acids are oleic acid, lauric acid, caprylic acid, palmitic acid, myristic acid, stearic acid, and capric acid. Either unsaturated or saturated acids may be used, singly or in mixtures. The acids selected should be one so as to produce an ester having a satisfactory gasoline solubility; a satisfactory fluidity at a temperature encountered in the intake manifold and a satisfactory stability. Preferred compounds comprise mono esters, particularly mono esters of pentaerythritol.

In order to further illustrate the invention, the following example is given:

Example Various operations were conducted employing a one cylinder air cooled Wisconsin internal combustion engine (AEH Model). The Wisconsin engine had a cylinder made of nitrated steel (metal of the type used in aircraft engines).

An aviation fuel having a clear octane number of and containing 3.94 cc. of tetraethyl lead per gallon and having the following Engler distillation was used in the various operations:

. i 3 The'leaded octane number was 96 A. S. T. M. and 98 Research. A lead scavenger agent comprising ethylene dibromide was added to the fuel in a concentration of one theory of halogen per theory of lead.

The operations were conducted in two stages. In the first stage of the operation the engine the engine was run for 8 hours on the fuel composition. In the second stage of the operation, the engine was dismantled and the cylinder placed in a humidity cabinet for five days. At the expiration of days, the extent of rusting of the interior surface of the cylinder was determined and recorded as, per cent rusting."

In operation A the aviation fuel containing the above identified quantity of lead and lead scavenger agent was run as described. In operation B the identical fuel composition was run except that 0.5% of mono oleate of pentaerythritol was used. In operation C 0.5% of tetra oleate of pentaerythritol was employed. The results of the respective operations were as follows:

The data illustrated in the table shows a 50% decrease in the extent of rusting when the mono oleate of pentaerythritol was added to the fuel.

4 The use of tetraoleate of pentaerythritol resulted in a very heavy deposit on the valve in the intake system of the engine. The extent of the deposit was such that the engine was on the verge of failing.

Having described the invention, it is claimed:

1. A process for inhibiting the rusting of the internal surfaces of internal combustion engines during periods of idleness after said surfaces had been exposed to combustion utilizing leaded motor fuels containing an organic halide scavenging agent which comprises burning in said engine prior to its period of idleness a motor fuel containing from about .01% to 1.0% by weight of a partial ester formed from an aliphatic polyhydroxy alcohol and at least one monocarboxylic acid which is characterized by containing from about 8 to 24 carbon atoms per molecule.

2. Process as defined by claim 1 wherein said motor fuel contains tetraethyl lead and wherein said ester comprises the pentaerythritol mono oleate.

3. The process defined by claim 1 wherein said aliphatic polyhydroxy alcohol is selected from the group consisting of pentaerythritol, di-

pentaerythritol, polyglycerol, sorbitol, polysorbitol, erythritol, mannitol, and sorbitan.

DILWORTH T. ROGERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,434,490 Duncan Jan. 13, 1948 2,479,424 Sproule et al Aug. 16, 1949 2,482,517 Schiermeier et a1. Sept. 20, 1949 2,527,889 Moore et al Oct. 31, 1950 

1. A PROCESS FOR INHIBITING THE RUSTING OF THE INTERNAL SURFACES OF INTERNAL COMBUSTION ENGINES DURING PERIODS OF IDLENESS AFTER SAID SURFACES HAD BEEN EXPOSED TO COMBUSTION UTILIZING LEADED MOTOR FUELS CONTAINING AN ORGANIC HALIDE SCAVENGING AGENT WHICH COMPRISES BURNING IN SAID ENGINE PRIOR TO ITS PERIOD OF IDLENESS A MOTOR FUEL CONTAINING FROM ABOUT .01% TO 1.0% BY WEIGHT OF A PARTIAL ESTER FORMED FROM AN ALIPHATIC POLYHYDROXY ALCOHOL AND AT LEAST ONE MONOCARBOXYLIC ACID WHICH IS CHARACTERIZED BY CONTAINING FROM ABOUT 8 TO 24 CARBON ATOMS PER MOLECULE. 